TheImprovement ofTropical and Subtropical Rangelands

OVERVIEW 7
higher levels of biological productivity were maintained throughout
similar past fluctuations in rainfall, until changes in land-UN patterns
occurred (National Research Council, 1983b). One ofthe most
significant changes was the introduction of large-lIC&1e cattle husbandry
in colonial Africa, and the subsequent control of the tsetse
fly in some areas by in&eeticides and by removing the vegetation of
the fly's habitats.
In the areas where this occurred (sub-Saharan W..t Africa, the
Hom of Africa, Botswana in southern Africa), a previously complex
ecosystem comprising trees, shrubs, and grauel, with a wide variety
of wildlife and livestock (camels, goats, sheep, and cattle), has become
progressively simplified. The remaining perennial browae trees
and shrubs and .grasses are subject to overgrazing.
The consequences of devegetation are most stark in arid and
semiarid areas, where they lead rapidly to erosion, eJ.imihation of
many useful species, and a drastic drop in carrying capacity, resulting
in death of animals and the drift of refugees to other areas. In
wetter agricultural areas, environmental consequences may not be so
dramatic, but the economic impact can be substantial because the
erosion-drought-flood cycle interferes with cropping.
In recent years, an additional factor has been the rising COlt of
petroleum fuels, which has led to a growing use of fuelwood. Much
of the fuelwood has been taken from areas surrounding agricultural
regions for local domestic use. However, fuelwood and charcoal are
increasingly being sold in towns to peripheral urban dwellers for
cooking as well as to commercial establishments for various usee.
Little of this additional demand has been met by increued planting
of commercial or state fuelwood lots (National Research Council,
1983a). The impact of the deforestation is being felt as reduced
moisture-holding capacity and increued exposure of soil and crops
to wind and rain cause lower yields of crops and 1088 of topsoil.
THE NEED FOR REHABllJTATION
Rangelands are easy to destroy, but difficult to restore. However,
because of their size and potential for increued productivity, their
improvement can bring many benefits to developing countries. If
left undisturbed, rangelands will, in most cases, regrow and reclothe
themselves with vegetation, but it may take more than 50 years
to return to a stable state. Opportunities should be seized that
emphasize vegetation for useful forage and conservation of species.